Fraser was part of the team that won silver at the European Championships last year, finishing fourth in the individual all-around final, but when it came to the British Championships in March, he could only pick up bronze in the parallel bars.
But he submitted the routine with the highest difficulty in the final to earn a score of 15.000 and GB's second gold medal in the space of 24 hours after Max Whitlock won pommel horse gold yesterday.
"It’s a dream come true! Unbelievable! World champion? It doesn’t get better," Fraser said.
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"All I was thinking was 'Get through it, stick the dismount' then score by score I was so nervous.
"I had a hope for a medal, but gold is crazy.
"I’ve worked really hard on the parallel bars and it’s paid off in the biggest way. World champion! Unreal."
Team GB's medal tally is now up to four after Whitlock's success, along with Ellie Downie's vault bronze and older sister Becky picking up silver on the uneven bars.
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